What Affects the Function of an Enzyme?

The Effects of pH on the Function of Catalase - Answer KeyObservations:Table 1: Results of a study of the effects of pH on enzyme behavior.Test performed pHTest result(+/-)Additional observationsWater 7 +Bubbles form around the potato.The slices float to the surface.Vinegar 2- 3 - No reaction occurs.0.1 M NaOH 13 - No reaction occurs.Detergent 10 – 11 +The reaction that occurs is notas vigorous as it is with water.Analysis:1. Enzymes are reaction specific. That is, they catalyze a specific chemicalreaction. Which lab observations permit you to infer that catalase acted on thehydrogen peroxide and not on the other solutions that were used in the lab?Bubbles did not form when the solutions were added. Bubbles formedonly after the hydrogen peroxide was added.2. The shape of a protein and its ability to function can be changed byenvironmental factors such as pH and temperature. Which laboratoryobservation permits you to infer that catalase contains a protein?The tests at the extreme pH values (acetic acid and sodium hydroxide)produced negative results while the other tests were positive.Application of principles1. Placing 3% hydrogen peroxide on a cut produces bubbles. What causes thebubbles to form in the wound, but not on the surrounding skin?The damaged cells around the wound release catalase (or some similarenzyme). The unbroken skin around the wound does not release catalase.2. Hydrogen peroxide is an effective antiseptic on surfaces but is less effectiveon a skin wound. Account for this difference.Since catalase is present at the site of a skin wound, hydrogen peroxide isbeing decomposed rapidly. Surfaces do not have enzymes and so thehydrogen peroxide lasts longer and can more effectively kill any bacteriain the area.3. When an apple is cut and left out for awhile, the wound turns brown becauseof the action of an enzyme found in the apple cells. Applying lemon juice (pH= 3) prevents the apple from turning brown. Use the results of your laboratoryinvestigation and your knowledge of enzymes to account for this.Enzyme action is affected by the pH of the environment. The result of theacetic acid test shows that a low pH prevents an enzyme fromfunctioning.

4. Dr. T.H. Oliver reported the first intravenous use of hydrogen peroxide in1920. Influenza patients were given hydrogen peroxide treatments with goodresults. What was accomplished by injecting the patients with hydrogenperoxide?Hydrogen peroxide, in the presence of catalase, was rapidly converted towater and oxygen. The oxygen level of the blood increased. Note: theanswers to problems 1 and 2 provide evidence for inferring that catalaseis present in the blood.Conclusions:1. State the pH range in which catalase can decompose hydrogen peroxide.Catalase decomposes hydrogen peroxide when the pH is between 3 and13.2. What environmental factors affect the rate at which an enzyme functions?Temperature, pH, and salinity affect the rate at which an enzymefunctions. The results of this lab demonstrate the effects of pH on theenzyme rate.3. How does the protein portion of an enzyme affect the behavior of the enzyme?Proteins have specific shapes that can be altered by environmental factorssuch as pH and temperature. Altering the shape of the protein also altersthe shape of the enzyme, affecting its behavior.